California Code, Vehicle Code - VEH § 24015

(a) Motorized bicycles shall comply with those federal motor vehicle safety standards established pursuant to Chapter 301 (commencing with Section 30101) of Part A of Subtitle VI of Title 49 of the United States Code that apply to a motor-driven cycle, as that term is defined in regulations adopted pursuant to those provisions.  These standards include, but are not limited to, provisions requiring a headlamp, taillamp, stoplamp, side and rear reflex reflectors, and adequate brakes.

(b) In addition to equipment required in subdivision (a), all motorized bicycles operated upon a highway shall be equipped with a mirror as required in subdivision (a) of Section 26709, a horn as required in Section 27000, and an adequate muffler as required in subdivision (a) of Section 27150.

(c) Except as provided in subdivisions (a) and (b), none of the provisions of this chapter relating to motorcycles and motor-driven cycles, as defined in this code, shall apply to a motorized bicycle.